JP2009209395A - Method and apparatus for forming thin film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve such a problem that, in a thin film forming process, when a large amount of deposit is adhered to a mask 4, the film deposition range regulated by the mask 4 is reduced, or a part of the deposit is peeled and detached and dropped on an evaporation source 2 to cause splash, and the deposit must be removed; however, the adhesiveness between the mask 4 and the deposit is strong, and any peeling method is necessary when the deposit is hardly peeled only by the vibration. <P>SOLUTION: A thin film forming method comprises: a step of forming a thin film; a step of dropping the temperature of the mask 4 below the temperature of the mask during the film deposition; a step of feeding oxygen to a deposit; and a step of removing the deposit. The deposit on the mask 4 is peeled and removed thereby. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a thin film formation method, and more particularly to a mask regeneration method by removing a mask deposit in a vacuum. The present invention also relates to a thin film forming apparatus using a mask.

  In recent years, the miniaturization and multi-functionalization of portable devices have progressed, and accordingly, the capacity of a battery as a power source for portable devices has been demanded.

  As a high-capacity negative electrode active material in a lithium battery, a material containing silicon (Si) is promising because it has a large amount of occlusion of lithium, and among them, there are many SiOx (0 <x <2) which is a compound of Si and oxygen (O). It is being considered. Methods for forming SiOx on a current collector include a method in which SiOx particles are mixed with a binder and a solvent to form a paste, which is applied, dried and rolled, and a vacuum evaporation method.

  Among these methods, the vacuum deposition method is a dry process that can obtain a negative electrode active material film that does not contain a binder and is advantageous for increasing the energy density.

  In order to improve productivity in the vacuum deposition process, it is effective to reduce the frequency of opening the vacuum chamber to atmospheric pressure. That is, a technique for performing film formation and film formation for a long time in one batch of vacuum deposition process is required. One of the techniques required for this is a mask regeneration technique in a vacuum.

  If a large amount of deposits adheres to the mask in the vacuum deposition process, the film formation range regulated by the mask will decrease, or a part of the deposits will peel off and fall off and fall to the evaporation source, causing splash (bumping). The problem that it ends up occurs. If the mask is regenerated by appropriately peeling and removing the mask deposit, the vacuum deposition process can be continued.

  Patent Document 1 discloses a method of peeling a deposit in a vacuum by irradiating a mask to which the deposit is attached with an energy beam that generates vibration.

Patent Document 2 discloses a method for producing a carbon powder by peeling a carbon film produced by a discharge reaction in a vacuum by vibration in a vacuum.
JP 2006-169573 A JP-A-10-297911

  In Patent Document 1, the mask is vibrated by irradiating a laser beam or the like on the mask deposit, and peeling occurs due to a difference in response to the vibration between the mask and the deposit. The deposit is an organic material, the mask is made of SUS, and the thickness of the deposit is disclosed as 0.08 to 0.1 μm. As for organic EL film deposited on a SUS mask, it is effective when it is separated only by vibration, but it describes the peeling method when the adhesion between the mask and the deposit is strong and it is difficult to separate only by vibration. It is not done.

Patent Document 2 describes a method in which powder adhered to a wall surface is separated by vibrating the wall surface by ultrasonic vibration. The adhering powder is carbon, and the wall surface is copper.
However, in order to peel off the deposit, it is a necessary condition that the adhesion between the wall surface and the deposit is weak, and there is no description of a method for peeling the deposit when the adhesion is strong and difficult to peel off.

  The present invention proposes a peeling method in which the adhesion between the mask and the deposit is somewhat strong and difficult to peel off by vibration alone. Another object of the present invention is to regenerate the mask by peeling and removing the mask deposit when necessary in one batch of the vacuum vapor deposition method, enabling long-time film formation and a large amount of film formation, and improving productivity.

  In order to solve the above-described problems, the thin film forming method of the present invention includes a first step of forming a thin film on a substrate, and a mask temperature lower than that in the first step after the first step. A second step, a third step for supplying oxygen to a deposit containing particles flying from an evaporation source deposited on the mask, simultaneously with the second step or after the second step, and a third step And a fourth step of removing deposits at the same time or after the third step.

  With this configuration, the mask / deposit interface is separated or cracked due to the difference in shrinkage due to the difference in linear expansion coefficient between the mask and the deposit, and further mask / deposition is caused by the expansion due to the oxidation reaction between the deposit and oxygen. By promoting peeling and cracking at the object interface, deposits that are difficult to peel off can be removed from the mask.

  Further, by performing the second step while applying a physical impact to the mask, the stress generated at the mask / deposit interface due to the difference in shrinkage can be caused to start a crack, thereby promoting peeling.

  Further, by performing the third step while applying a physical impact to the mask, the stress generated at the mask / deposit interface due to the expansion of the deposit can cause a starting point of cracking and promote the peeling.

  Further, since the fourth step of removing the deposit is based on physical impact, the deposit can be effectively removed in a vacuum with a simple configuration.

The deposit of the present invention is preferably composed mainly of SiOx (0 <x <2). According to this configuration, the linear expansion coefficient (at a temperature of 500 K) is 3.5 × 10 ⁻⁶ K ^{−1 for} Si and about 0.6 × 10 ⁻⁶ K ⁻¹ for quartz (SiO ₂ ), for example, 17.17 for SUS. It is 5 × 10 ⁻⁶ K ⁻¹ , and the difference in linear expansion coefficient between SiOx and SUS is large, and the large shrinkage difference when the mask is cooled promotes peeling at the mask / deposit interface. Further, SiOx is easily oxidized by being exposed to an oxygen atmosphere, and the larger the oxidation ratio, the larger the expansion, so that peeling at the mask / deposit interface can be promoted.

  The second step of the present invention is preferably performed by moving the shutter between the evaporation source and the mask. According to the present invention, it is possible to prevent both the radiant heat energy from the evaporation source and the thermal energy carried by the flying particles from reaching the mask. Are better.

  Furthermore, when the shutter of the present invention is between the evaporation source and the mask, the shutter may be convex downward. With this configuration, it is possible to prevent deposits that have been peeled off and removed from the mask from falling on the shutter and falling into the evaporation source, thus preventing splash caused by deposits falling on the evaporation source and ensuring stable operation. This makes it possible to perform the vacuum deposition process, which is excellent in productivity.

In the second step of the present invention of the present invention, it is desirable to flow a plurality of refrigerants (brine) having different temperatures through the pipe attached to the mask at different times. With this configuration, the temperature of the mask and the deposit can be controlled with a simple configuration, and peeling at the interface between the mask and the deposit is promoted according to a difference in linear expansion coefficient between the mask and the deposit by causing a heat cycle.

  Further, the present invention relates to a vacuum evaporation apparatus having a chamber, an evaporation source, a substrate, and a mask, a means for lowering the temperature of the mask, a means for supplying oxygen to the deposit deposited on the mask, and a mask The present invention also relates to a thin film forming apparatus having means for giving a physical impact to the film.

  According to the vacuum vapor deposition method of the present invention, it is possible to peel and remove deposits in a vacuum that have a certain degree of adhesion between the mask and the deposits and that are difficult to peel off by vibration alone. Therefore, productivity can be improved by performing film formation and film formation for a long time in one vacuum process batch.

  Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1)
Fig.1 (a) is a figure which shows the outline | summary of the vacuum evaporation system of this invention.

  In FIG. 1A, the inside of the chamber 1 is evacuated, and when the evaporation source 2 is ready to form a film, the shutter 5 is changed from the state shown in FIG. 1A to the state shown in FIG. Move to start film formation on the substrate 3. Between the evaporation source 2 and the substrate 4, a mask 4 for restricting the film forming range is arranged. The film formation is interrupted by moving the shutter 5 between the evaporation source 2 and the substrate 3 as shown in FIG. The mask 4 is provided with an impact applying device 6, and an oxygen nozzle 7 for supplying oxygen gas is disposed on the mask 4 on the evaporation source 2 side.

  The substrate 3 is a long foil unwound from the unwinding roll 8, and for example, a copper foil can be used. It moves from the roll 9 to the roll 10 and winds around the take-up roll 11. When the substrate 3 passes through the opening range of the mask 4 between the roll 9 and the roll 10, vapor deposition particles are formed on the substrate 3. The evaporation source 2 is configured by disposing an evaporation material in a carbon crucible, and is disposed in a water-cooled copper hearth so that the carbon crucible is damaged by being too hot and oxidizing. To prevent. For example, Si is used as the evaporation material. The evaporation source 2 is heated by an electron beam (not shown). The chamber 1 is evacuated using a vacuum pump 13 via an evacuation pipe 12.

  A metal plate can be used as the mask 4 of the present invention, and for example, SUS304 or SUS316 can be used. SUS304 and SUS316 are suitable as long as they are 900 ° C. or lower, since they hardly oxidize even in air with a high oxygen concentration and are excellent in oxidation resistance at high temperatures. A copper pipe (not shown) through which water flows is attached to the mask 4, and the water is cooled so that the temperature of the water is controlled to 20 ° C. at a portion where the water is introduced into the mask 4 so that the mask 4 does not exceed 900 ° C. To do.

  The method of lowering the temperature of the mask of the present invention is performed by moving the shutter 5 between the evaporation source 2 and the mask 4. When the evaporation material is Si, the evaporation material of the evaporation source 2 needs to be about 2000 ° C., and the mask 4 receives a lot of heat due to radiation heat and deposition of particles flying from the evaporation source 2. By moving the shutter 5 between the evaporation source 2 and the mask 4, it is possible to prevent both radiant heat and heat received by deposition of particles flying from the evaporation source 2. The mask 4 is a copper pipe attached to the mask 4. It is cooled until it approaches 20 ° C., which is the temperature of the water flowing through.

  As the shutter 5, for example, a SUS-made one can be used, and a downwardly convex shape as shown in FIG. 1 is suitable. Splash is likely to occur if deposits that fall off the mask 4 fall into the evaporation source 2 below the mask 4, but the deposits are collected on the upper surface of the shutter 5, and the deposits are moved by moving the shutter 5. Can be removed from the evaporation source 2 by moving it to a different location from the evaporation source 2 and removing it. By moving the deposit by the shutter 5, the mask can be regenerated a plurality of times.

  The oxygen supply method to the deposit of the present invention can be performed by blowing oxygen gas from the oxygen nozzle 7 toward the deposit. The oxygen nozzle 7 can be configured by forming holes in a metal tube at regular intervals.

  As the impact applying means of the present invention, a vibrator HV-00 manufactured by Murata Seiko Co., Ltd. can be used as the impact applying device 6. The vibrator bar end can be attached to the mask 4 and vibrated, whereby a mechanical shock can be applied to the mask 4.

  In order to effectively remove the deposit from the mask 4 according to the present invention, the larger the temperature difference between the mask 4 and the deposit, the more effective the linear expansion coefficient difference between the mask 4 and the deposit. On the other hand, the mask 4 is distorted and deformed at a high temperature, although it depends on the material and processing method. Therefore, it is desirable to set the temperature of the mask 4 to a certain value or less during film formation. From the above points, the temperature difference when the mask 4 is set to a lower temperature than during film formation is preferably 150 ° C. or higher and 700 ° C. or lower, and more preferably 300 ° C. or higher and 600 ° C. or lower.

In order to effectively remove deposits from the mask 4 according to the present invention, it is effective to expand the deposits by oxidizing them more. In order to oxidize the deposit, it is effective to supply a large amount of oxygen near the deposit and raise the oxygen partial pressure near the deposit. On the other hand, if a large amount of gas is supplied into the vacuum chamber, the degree of vacuum is lowered and the vacuum pump is damaged. Therefore, it is desirable that the degree of vacuum at the inlet of the vacuum pump be a certain value or less. From the above points, the degree of vacuum at the inlet of the vacuum pump when oxygen is supplied to the deposit is preferably 1 × 10 ⁻² Pa (Pa: Pascal) to 1 Pa, and more preferably 5 × 10 ⁻² Pa to 2 × 10 ⁻¹ Pa. .

(Embodiment 2)
FIG. 2 is a diagram showing an outline of a vacuum deposition apparatus including the mask regeneration method of the present invention.

  In addition, the same code | symbol is used about the same structure as Embodiment 1, and description is abbreviate | omitted.

  Two copper pipes (not shown) for flowing two types of brine are attached to the mask 4 of the present invention, and water and Etabline EC-Z made by Tokyo Fine Chemical are used for the brine. The temperature of water is controlled to 20 ° C., the temperature of the Etabline EC-Z is controlled to −40 ° C., and the temperature of the mask 4 can be controlled from 20 ° C. to −40 ° C. by alternately flowing at intervals of 1 minute.

  As the impact applying means of the present invention, a metal wire brush is attached to the rotating shaft of the motor as the impact applying device 6, and the deposited brush on the mask 4 is scanned while contacting the rotated brush with the mask 4, The mask 4 may be configured to give a mechanical impact.

(Embodiment 3)
FIG. 3 is a diagram showing an outline of a vacuum deposition apparatus including the mask regeneration method of the present invention.

  In addition, the same code | symbol is used about the same structure as Embodiment 1, and description is abbreviate | omitted.

  As the impact applying means of the present invention, the impact applying device 6 can be configured by attaching an eccentric weight to the rotating shaft of a motor and causing the eccentric weight to collide with the mask by rotation to apply a mechanical impact to the mask.

  In Embodiments 1 to 3, the vacuum vapor deposition method has been described. However, other thin film forming methods such as a sputtering method and a CVD method have the same effect and can be similarly applied.

(Example)
The vacuum vapor deposition apparatus shown in FIGS. 1 (a) and 1 (b) was used.

  The evaporation source 2 was configured by crushing a single crystal Si ingot made of high-purity chemical as an evaporation material into a size of about 1 cm and putting it into a lump into a carbon crucible. The carbon crucible was heated with an electron beam (not shown) while being cooled with a copper hearth (not shown). The electron beam conditions during heating were an acceleration voltage of -13 kV and an emission current of 1A.

  The substrate 3 is made of a roughened electrolytic copper foil (thickness 35 μm) manufactured by Furukawa Circuit Foil Co., Ltd., unwound from the unwinding roll 8, passed through the roll 9 and the roll 10, and then into the winding roll 11. The substrate is moved by winding.

  The mask 4 was produced by processing a 2 mm thick SUS304 plate. A copper pipe (not shown) was attached to the mask 4 by welding, and water controlled at 20 ° C. was allowed to flow.

  The surface on which the mask deposit was deposited was processed into a rough surface with a surface roughness Ra = 0.2 μm. If Ra = 0.1 μm or less, a phenomenon in which the deposits are peeled off or dropped off from the mask by depositing several μm to several tens of μm is not suitable. Here, the surface roughness Ra was measured using an ultra-deep microscope VK-8500 manufactured by Keyence, and calculated according to JIS B 0601-1994 surface roughness.

  The shutter 5 was produced by processing a 5 mm thick SUS304 plate into an arc shape shown in FIG. A copper pipe (not shown) was attached to the shutter 5 by welding, and water controlled at 20 ° C. was allowed to flow. The shutter 5 is designed to move like a pendulum and is in the position shown in FIG. 1B during film formation. When the film formation is interrupted and the deposit is peeled off and removed, the shutter 5 is in the position shown in FIG. is there.

  The impact applying device 6 is configured such that an eccentric weight is attached to the shaft of the motor and is rotated at a frequency of 10 times / second with an output of 10 W to collide with the mask 4.

The oxygen nozzle 7 was produced by opening holes of φ0.5 mm at intervals of 2 cm in a SUS 1/4 inch tube. The flow rate of oxygen gas was controlled by a mass flow controller, and 50 sccm was flowed during film formation on the substrate 3, and 700 sccm was flowed during peeling of the deposit. The degree of vacuum during film formation was 5 × 10 ⁻³ Pa, and the degree of vacuum during peeling of the deposit was ¹ × 10 ⁻¹ Pa.

  During film formation, the temperature of the mask 4 rose, and it reached 500 ° C. or more in a place closest to the evaporation source 2 and where the deposit deposition rate was large. As shown in FIG. 1A, the mask 5 was cooled by moving the shutter 5 between the evaporation source 3 and the mask 4, and the temperature became close to 20 ° C. over time. Depending on the location of the mask, a temperature difference of about 200 to 500 ° C. was generated during film formation and during cooling.

After film formation for a predetermined time, the shutter 5 is moved from the position shown in FIG. 1B to the position shown in FIG. Then, oxygen gas was sprayed from the oxygen nozzle 7 toward the mask. As a result, the deposits peeled off and dropped on the shutter 5. The separated deposit was about 1 to 30 mm in size and curved. The separated deposits are treated with EPMA (Electron Probe Micro).
When analyzing the composition using an analyzer, the mole ratio O / Si between O and Si is 0.96 in the separated interface side portion, and the mole ratio O / Si between O and Si other than the interface side portion is 0.35. Met.

The separated interface side of the peeled deposit is removed by SEM (Scanning Electron).
The results observed by Microscope are shown in FIG. Many cracks of about several tens of μm and fine cracks of 1 μm or less were observed on the peeled interface. When the mask 4 and the deposit are cooled, it is considered that a difference in shrinkage according to the difference in linear expansion coefficient occurs, and as a result, a stress is generated at the interface between the mask 4 and the deposit to generate a crack. It is presumed that the surface area was greatly increased due to the generation of many cracks, and as a result, the oxidation rate when oxygen was supplied increased. It is presumed that the deposit was greatly expanded due to the increase in the oxidation rate and promoted peeling at the interface between the mask 4 and the deposit.

  The method for regenerating a mask of a vacuum evaporation apparatus according to the present invention can be used in a film forming apparatus in which deposits adhere to a mask by film formation over a long time and a large amount of film formation. Deposits that are difficult to peel off by vibration alone can be peeled and removed in a vacuum, so that film formation can be continued. Therefore, productivity can be improved.

(A) The figure which shows the outline | summary of the vacuum evaporation system containing the mask reproduction | regeneration method at the time of stopping the film-forming in Embodiment 1 of this invention, and peeling and removing a deposit, (b) The mask reproduction | regeneration method during film-forming The figure which shows the outline of the vacuum evaporation system including The figure which shows the outline | summary of the vacuum evaporation system containing the mask reproduction | regeneration method in Embodiment 2 of this invention. The figure which shows the outline | summary of the vacuum evaporation system containing the mask reproduction | regeneration method in Embodiment 3 of this invention. SEM photograph of peeling interface side of peeled deposit in Example

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vacuum chamber 2 Evaporation source 3 Board | substrate 4 Mask 5 Shutter 6 Impact application apparatus 7 Oxygen nozzle 8 Unwinding roll 9 Roll 10 Roll 11 Winding roll 12 Vacuum piping 13 Vacuum pump

Claims (9)

In the thin film formation method of forming a thin film by regulating the particles flying from the evaporation source in vacuum with a mask and attaching them to the substrate,
A first step of forming the thin film on the substrate;
After the first step, a second step in which the temperature of the mask is lower than that during the first step;
A third step of supplying oxygen to a deposit containing particles flying from the evaporation source deposited on the mask simultaneously with the second step or after the second step;
A fourth step of removing the deposit simultaneously with the third step or after the third step;
A thin film forming method characterized by comprising:   The thin film forming method according to claim 1, wherein the second step is performed while applying a physical impact to the mask.   The thin film forming method according to claim 1, wherein the third step is performed while applying a physical impact to the mask.   The thin film forming method according to claim 1, wherein the fourth step of removing the deposit is by physical impact.   2. The thin film forming method according to claim 1, wherein the deposit contains SiOx (0 <x <2) as a main component.   The thin film forming method according to claim 1, wherein the second step is performed by moving a shutter between the evaporation source and the mask.   7. The method of forming a thin film according to claim 6, wherein when the shutter is between the evaporation source and the mask, the shutter has a downwardly convex shape.   2. The thin film forming method according to claim 1, wherein the second step is performed by flowing a plurality of brines having different temperatures through pipes attached to the mask at different times and changing the mask temperature.   In a thin film forming apparatus having a vacuum chamber, an evaporation source, a substrate, and a mask, means for lowering the temperature of the mask, means for supplying oxygen to the deposit deposited on the mask, and the mask And a means for giving a physical impact to the thin film forming apparatus.

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